If y varies with x, and y equals 10 when x equals 4, find when y equals 80

1) if x^2=40, what is the value of x? a) +- 80 b) +- 20 c) +- square root of 80 d) +- square root of 40 2) solve x^2= -169 a) undefined b) 13 c) +- 13 d) -13 3) a square rug covers 79 square feet of floor. what is the approximate length of one side of the rug? (approximate to the nearest hundredth foot) a) 8.86 feet b) 8.87 feet c) 8.88 feet d) 8.89 feet